User terminal, radio base station and radio communication method

ABSTRACT

The present invention is designed reduce the increase of load in user terminals even when the number of CCs that can be configured in a user terminal is expanded from that of existing systems and/or when CA is executed using unlicensed CCs. A user terminal communicates with a radio base station by means of carrier aggregation using a plurality of component carriers (CCs), and has a receiving section that receives DL signals transmitted from each CC, a measurement section that makes measurements by using the DL signals, and a control section that controls the receiving operations in the receiving section and the measurement operations in the measurement section, and, when a plurality of CCs, including at least a first CC, which corresponds to a primary CC of an existing system, and a third CC, which is different from the first CC and a second CC that corresponds to a secondary CC of the existing system, are configured, the control section applies, to the third CC, receiving operations and/or measurement operations that are different from those of the second CC.

TECHNICAL FIELD

The present invention relates to a user terminal, a radio base stationand a radio communication method in next-generation mobile communicationsystems.

BACKGROUND ART

In the UMTS (Universal Mobile Telecommunications System) network, thespecifications of long term evolution (LTE) have been drafted for thepurpose of further increasing high speed data rates, providing lowerdelays and so on (see non-patent literature 1). Successor system ofLTE—referred to as “LTE-advanced” (also referred to as “LTE-A”)—havebeen under study for the purpose of achieving further broadbandizationand increased speed beyond LTE, and the specifications thereof have beendrafted as LTE Rel. 10 to 12.

The system band in LTE Rel. 10 to 12 includes at least one componentcarrier (CC), where the LTE system band constitutes one unit. Suchbundling of a plurality of CCs into a wide band is referred to as“carrier aggregation” (CA). Also, in LTE Rel. 12 supports dualconnectivity (DC), in which a user terminal communicates by using CCsthat are controlled separately by different radio base stations(schedulers).

In CA/DC in the above-mentioned successor systems of LTE (LTE Rel. 10 to12), the maximum number of CCs that can be configured per user terminal(UE) is limited to five. With LTE of Rel. 13 and later versions, whichare more advanced successor systems of LTE, studies are in progress tomitigate the limit of the number of CCs that can be configured in a userterminal and to configure six or more CCs (for example, 32 CCs), inorder to makes possible more flexible and faster communication.

The specifications of LTE Rel. 8 to 12 have been drafted assumingexclusive operations in frequency bands that are licensed tooperators—that is, licensed bands. As licensed bands, for example, 800MHz, 2 GHz and/or 1.7 GHz are used.

Furthermore, for future radio communication systems (Rel. 13 and laterversions), a system (“LTE-U” (LTE Unlicensed)) to run LTE systems notonly in frequency bands licensed to communications providers (operators)(licensed bands), but also in frequency bands where license is notrequired (unlicensed bands), is under study. In particular, a system(LAA: Licensed-Assisted Access) to run an unlicensed band assuming thepresence of a licensed band is also under study. Note that systems thatrun LTE/LTE-A in unlicensed bands may be collectively referred to as“LAA.” A licensed band is a band in which a specific provider is allowedexclusive use, and an unlicensed band is a band which is not limited toa specific provider, and in which radio stations can be provided.

An unlicensed band may be run without even synchronization, coordinationand/or cooperation between different operators and/or non-operators, andthere is a threat that significant cross-interference is produced incomparison to a licensed band. Consequently, when an LTE/LTE-A system(LTE-U) is run in an unlicensed band, it is desirable if the LTE/LTE-Asystem operates by taking into account the cross-interference with othersystems that run in unlicensed bands such as Wi-Fi, other operators'LTE-U, and so on. In order to prevent cross-interference in unlicensedbands, a study is in progress to allow an LTE-U base station/userterminal to perform “listening” before transmitting a signal and limitthe transmission depending on the result of listening.

Also, for unlicensed bands, for example, the 2.4 GHz band and the 5 GHzband where Wi-Fi (registered trademark) and Bluetooth (registeredtrademark) can be used, and the 60 GHz band where millimeter-wave radarscan be used are under study for use. Studies are in progress to usethese unlicensed bands in small cells.

CITATION LIST Non-Patent Literature

Non-Patent Literature 1: 3GPP TS 36.300 “Evolved Universal TerrestrialRadio Access (E-UTRA) and Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN); Overall Description; Stage 2”

SUMMARY OF INVENTION Technical Problem

CA/DC for use in systems according to LTE Rel. 10 to 12 supports oneprimary cell (“PCell,” “PCC,” etc.) and maximum four secondary cells(“SCells,” “SCCs,” etc.) as cells (CCs) to configure in a user terminal.In this way, in CA for existing systems (LTE Rel. 10 to 12), the numberof CCs that can be configured per user terminal (UE) is limited tomaximum five.

Meanwhile, when the number of CCs that can be configured in a userterminal is expanded to six or above (for example, 32 CCs) in moreadvanced successor systems of LTE (for example, LTE Rel. 13 and laterversions), the load of the user terminal might grow following theincrease of the number of CCs. For example, when additional CCs(“expanded CCs”) are configured in a user terminal as SCCs, the loadthat is required of the user terminal for the measurement (RRMmeasurements, CSI measurements, etc.) operations for each SCC, the DLsignal receiving operations, and so on is likely to grow.

Also, when an unlicensed CC is configured in a user terminal as an SCC(for example, an as an expanded CC), cases might occur where, dependingon the result of listening (the result of LBT), the user terminal isunable to transmit and receive signals with the unlicensed CC on aregular basis. Consequently, if the user terminal tries to perform themeasurement operations, receiving operations and so on for theunlicensed CC as for SCCs (SCells) of existing systems, unnecessaryoperations might increase, and there is a threat of increasing the userterminal's load.

The present invention has been made in view of the above, and it istherefore an object of the present invention to provide a user terminal,a radio base station and a radio communication method that can reducethe increase of load on user terminals even when the number of CCs thatcan be configured in a user terminal is expanded from that of existingsystems and/or when CA is executed using unlicensed CCs.

Solution to Problem

One aspect of the present invention provides a user terminal thatcommunicates with a radio base station by means of carrier aggregationusing a plurality of component carriers (CCs), and this user terminalhas a receiving section that receives DL signals transmitted from eachCC, a measurement section that makes measurements by using the DLsignals, and a control section that controls the receiving operations inthe receiving section and the measurement operations in the measurementsection, and, in this user terminal, when a plurality of CCs, includingat least a first CC, which corresponds to a primary CC of an existingsystem, and a third CC, which is different from the first CC and asecond CC that corresponds to a secondary CC of the existing system, areconfigured, the control section applies, to the third CC, receivingoperations and/or measurement operations that are different from thoseof the second CC.

Advantageous Effects of Invention

According to the present invention, the increase of load on userterminals can be reduced even when the number of CCs that can beconfigured in a user terminal is expanded from that of existing systemsand/or when CA is executed using unlicensed CCs.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram to explain an overview of carrier aggregation insuccessor systems of LTE;

FIG. 2 is a diagram to show an example of transmission control for usewhen listening (LBT) is used;

FIG. 3 is a diagram to explain CA using a PCC and SCCs of an existingsystem, and an unlicensed CC;

FIG. 4 is a diagram to show an example of a case where unlicensed CCsare configured as SCCs;

FIG. 5 is a diagram to show an example of carrier aggregation in whichTCCs are used;

FIG. 6 provide diagrams to show an example of measurement operations fora TCC;

FIGS. 7 provide diagrams to show examples of receivingoperations/measurement operations for a TCC;

FIG. 8 is a diagram to show another example of carrier aggregation inwhich TCCs are used;

FIG. 9 is a diagram to show an example of a schematic structure of aradio communication system according to the present embodiment;

FIG. 10 is a diagram to show an example of an overall structure of aradio base station according to the present embodiment;

FIG. 11 is a diagram to show an example of a functional structure of aradio base station according to the present embodiment;

FIG. 12 is a diagram to show an example of an overall structure of auser terminal according to the present embodiment; and

FIG. 13 is a diagram to show an example of a functional structure of auser terminal according to the present embodiment.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is a diagram to explain carrier aggregation (CA). As shown inFIG. 1, in CA of existing systems (up to LTE Rel. 12), maximum fivecomponent carriers (CCs) (CC #1 to CC #5), where the system band of LTERel. 8 constitutes one unit, are bundled. That is, in carrieraggregation up to LTE Rel. 12, the number of CCs that can be configuredin a user terminal (UE: User Equipment) is limited to maximum five (oneprimary cell and maximum four secondary cells).

The primary cell (PCell, PCC, etc.) refers to the cell that manages RRCconnection, handover and so on when CA/DC is used, and is also a cellthat requires UL communication in order to receive data and feedbacksignals from terminals. The primary cell is always configured in boththe uplink and the downlink. A secondary cell (SCell, SCC, etc.) refersto another cell that is configured apart from the primary cell whenCA/DC is used. A secondary cell may be configured in the downlink alone,or may be configured in both the uplink and the downlink at the sametime.

Meanwhile, in more advanced successor systems of LTE (for example, LTERel. 13 and later versions), a study is in progress to soften the limitof the number of CCs that can be configured per user terminal, and useenhanced carrier aggregation (CA enhancement), in which six or more CCs(cells) are configured. For example, as shown in FIG. 1, when 32 CCs (CC#1 to CC #32) are bundled, a bandwidth of maximum 640 MHz can besecured. In this way, more flexible and faster radio communication isexpected to be made possible by increasing the number of CCs that can beconfigured in a user terminal.

Furthermore, for more advanced successor systems of LTE (for example,Rel. 13 and later versions), systems to run LTE systems not only infrequency bands licensed to communications providers (operators)(licensed bands), but also in frequency bands where license is notrequired (unlicensed bands), are under study.

The premise of existing LTE/LTE-A is that it is run in licensed bands,and therefore each operator is allocated a different frequency band.However, unlike a licensed band, an unlicensed band is not limited touse by a specific provider. When run in an unlicensed band, LTE may becarried out without even synchronization, coordination and/orcooperation between different operators and/or non-operators. In thiscase, a plurality of operators and/or systems share and use the samefrequency in the unlicensed band, and therefore there is a threat ofproducing cross-interference.

In Wi-Fi systems that are run in unlicensed bands, carrier sensemultiple access/collision avoidance (CSMA/CA), which is based on themechanism of LBT (Listen Before Talk), is employed. To be more specific,for example, a method, whereby each transmission point (TP), accesspoint (AP), Wi-Fi terminal (STA: Station) and so on perform “listening”(CCA: Clear Channel Assessment) before carrying out transmission, andcarries out transmission only when there is no signal beyond apredetermined level, is used. When there is a signal to exceed apredetermined level, a waiting time (backoff time) is provided, which isdetermined on a random basis, and, following this, listening isperformed again (see FIG. 2).

So, for LTE/LTE-A systems that are run in unlicensed bands (for example,LAA), too, a study is in progress to use transmission control based onthe result of listening. For example, a radio base station and/or a userterminal perform listening (LBT) before transmitting signals in anunlicensed band cell, and checks whether other systems (for example,Wi-Fi) and/or other operators are communicating. If, as a result oflistening, the received signal intensity from other systems and/or otherLAA transmission points is equal to or lower than a predetermined value,the radio base station and/or the user terminal judge that the channelis in the idle state (LBT_idle) and transmit signals. On the other hand,if, as a result of listening, the received signal intensity from othersystems and/or other LAA transmission points is greater than thepredetermined value, the radio base station and/or the user terminaljudge that the channel is in the busy state (LBT_busy), and limit signaltransmission.

Note that “listening” herein refers to the operation which radio basestations and/or user terminals perform before transmitting signals inorder to check/measure whether or not signals to exceed a predeterminedlevel (for example, predetermined power) are being transmitted fromother transmission points. Also, this “listening” performed by radiobase stations and/or user terminals may be referred to as “LBT” (ListenBefore Talk), “CCA” (Clear Channel Assessment), and so on. As to how tolimit signal transmission based on the result of LBT, possible methodsinclude making a transition to another carrier by way of DFS (DynamicFrequency Selection), applying transmission power control (TPC), holding(stopping) signal transmission, and so on.

In this way, by using LBT in communication in LTE/LTE-A (for example,LAA) systems that are run in unlicensed bands, it becomes possible toreduce the interference with other systems and so on.

Now, as shown in FIG. 1, expanding the number of CCs is effective towiden the band in carrier aggregation (LAA: License-Assisted Access)between licensed bands and unlicensed bands. For example, five licensedband CCs (=100 MHz) and fifteen unlicensed band CCs (=300 MHz) arebundled, and a bandwidth of 400 MHz can be secured.

Meanwhile, when the number of CCs that can be configured in a userterminal is expanded, and/or when CA is executed using an unlicensed CC(UCC), how to configure the expanded CCs and/or the unlicensed CC (UCC)and how to control the user terminal's operations is the problem (seeFIG. 3).

For example, as shown in FIG. 4, it may be possible to execute CA,assuming that an unlicensed CC (UCC: Unlicensed Component Carrier) is asecondary cell (SCC) of an existing system. Note that the unlicensed CC(UCC) in FIG. 4 may be configured as an expanded CC as well.

However, the transmission/non-transmission (ON/OFF) state in anunlicensed CC changes dynamically, because pre-transmission LBT is thepremise of unlicensed carriers. Consequently, there is a threat thatuser terminals are unable to transmit signals on a regular basis as inthe PCC or in SCCs in the activated state. On the other hand, in UCCs,although signals are not transmitted on a regular basis, signals startbeing transmitted or received soon depending on the result of LBT, sothat it is necessary to control user terminals to be able to transmitand receive these signals. In this way, the present inventors havefocused on the fact the user terminal operations that are required byUCCs are different from those required by existing activated state ornon-SCCs in the activated state.

Also, unlicensed bands generally have a wide band, and may be used asexpanded CCs according to Rel. 13 and later versions. In this case, asshown in FIG. 4, controlling expanded CCs (for example, UCCs) in thesame way as existing SCCs might result in increasing the load on theuser terminal end. For example, in order to quickly start communicatingin multiple CCs, a user terminal may configure a plurality of SCCsfirst, and, after executing measurement operations (for example, RRMmeasurements) for the SCCs in the deactivated state, activate an SCC ofgood quality, and start communicating. However, if many CCs that areconfigured in a user terminal are subjected to measurements as inmeasurements for existing PCCs and SCCs, the load upon user terminalsincreases in proportion to the number of CCs configured.

Also, since an unlicensed carrier allows co-presence with other systems,the quality varies significantly compared to a licensed carrier, and thereliability of communication is highly likely to deteriorate.Consequently, in LAA, it may be possible to support communication in anunlicensed carrier by using a licensed carrier (for example, report LBTresults by using the licensed carrier). In this case, the user terminaloperations required by unlicensed CCs may be different from thoserequired by existing SCCs.

So, the present inventors have come up with the idea of applyingoperation/control to user terminals differently between expanded CCs andunlicensed CCs, and existing PCCs and SCCs. Also, the present inventorshave come up with the idea of configuring a new CC that is neither a PCCnor an SCC, and configuring/reporting this CC to a user terminal, so asto enable the user terminal to distinguish the CC (for example, a UCC),to which different operations/control are applied, from the PCCs andSCCs of existing systems (Rel. 10 to 12).

To be more specific, the present inventors have come up with the idea ofdefining expanded CCs and/or UCCs differently from existing PCCs andSCCs, and applying different control/operations from those of existingSCCs (see FIG. 5). In this description, a CC, to which differentcontrol/operations from those of PCCs and SCCs of existing systems (Rel.10 to Rel. 12) are applied, will be referred to as a “TCC” (TertiaryCC), a “TCell,” a “third CC” or a “third cell” (hereinafter “TCC”). ATCC can be constituted by a licensed CC and/or an unlicensed CC.

A user terminal, in which a TCC is configured, can apply differentcontrol/operations (for example, measurement operations, receivingoperations, etc.) to the TCC, from those for SCCs (see FIG. 5). Forexample, the user terminal can perform different receiving operations(including, for example, downlink control information (DCI) and/orreference signal receiving processes) with respect to the TCC, fromthose for PCCs and SCCs. Also, the user terminal can apply differentmeasurement operations (measurement method, measurement conditions(requirements, etc.) to the TCC, from those of PCCs and SCCs.

By this means, even when many CCs are configured in a user terminal, itis still possible to reduce the increase of load in user terminals byapplying simple control and/or measurement operations to the TCCs. Also,when an unlicensed CC is configured in a user terminal as a TCC, byapplying UL transmission operations that take LBT into account (and thatare therefore different from those applied to PCCs and SCCs) to the TCC,it becomes possible to reduce wrong operations that arise from LBTresults, and allow adequate communication.

Now, the present embodiment will be described below in detail. Notethat, although cases will be described in the following descriptionwhere one or more licensed CC and/or unlicensed CCs are configured asTCCs, this is by no means limiting. For example, TCCs can be constitutedby unlicensed CCs alone. Also, with the present embodiment, it isequally possible to configure a PCC (PCell) and a TCC (TCell) in a userterminal and execute CA/DC (that is, SCCs (SCells) are not configured).Also, it is possible to configure five or more CCs in a user terminal asSCCs (SCells). Also, UL LBT and/or DL LBT can be used not only inunlicensed band, but also in licensed bands as well.

First Example

A case will be described with a first example where the measurementoperations and receiving operations which a user terminal applies to aTCC (TCell) are different from those for PCCs (PCells) and SCCs (SCells)of existing systems. Also, examples of measurement operations/receivingoperations for a TCC will be described below, assuming the case in whicha TCC is in the activated state (activated TCC), the case in which a TCCis in the deactivated state (deactivated TCC), and the case in which aTCC is not configured in the activated state/deactivated state.

<Deactivated State>

When a TCC is configured in a user terminal but is in the deactivatedstate (deactivated), a user terminal can measure the TCC (deactivatedTCC) based on different conditions (requirements) from those used in PCCand/or SCC measurements.

In an existing system, a user terminal makes measurements for an SCC inthe deactivated state (for example, RRM (Radio Resource Measurement)measurements), and reports the measurement results to a radio basestation. Based on the measurement results reported from the userterminal and so on, the radio base station controls the SCC'sconfiguration state (the activated state or the deactivated state) andso on.

According to the present embodiment, a user terminal makes measurementswith respect to TCCs in the deactivated state in the same way as withSCCs, but it is also possible to make the measurement conditions forTCCs softer than the conditions for SCCs. For example, a user terminalcan make the measurement conditions (the measurement period, themeasurement cycle, etc.) for TCCs softer than those of PCCs and/or SCCs,and execute measurements accordingly.

For example, a user terminal can configure a longer measurement cycleand/or a shorter measurement period in a TCC than in an SCC, and makemeasurements for the TCC (see FIG. 6A). In FIG. 6A, a case is shown inwhich a user terminal makes measurements for an SCC in a regular cycle(for example, every 40 ms), but makes measurements for a TCC in a longercycle.

By this means, it is possible to simplify the measurement operations forthe TCC, and reduce the user terminal's load. Note that the measurementcycles of the SCC and the TCC are not limited to the configurationsshown in FIG. 6A, and can be configured as appropriate. Also,information about the TCC's measurement cycle and so on may be set forthin the specification in advance, or may be reported from the radio basestation to the user terminal by using a predetermined CC (for example,the PCC and/or an SCC). Also, the user terminal may be structured tomeasure the TCC by applying the same conditions as those of the SCC, andconfigure the cycle of reporting the TCC's measurement results(transmission cycle) long.

Also, the user terminal can measure the TCC by softening the CC (cell)level to be detected and/or the reliability of measurements. The celllevel to be detected is also referred to as a “side condition,” and, forexample, the lower-limit SINR value is this.

Assuming an existing system with a PCC and an SCC, the cells'lower-limit SINR value which a user terminal should detect is stipulatedto be −6 dB, and the reliability (accuracy) of measurements is ±6 dB orless (within ±6 dB) (see FIG. 6B). So, with the present embodiment, thelower-limit SINR value which a user terminal should detect for a TCC canbe configured greater than −6 dB (for example, +3 dB). Alternatively,the reliability of measurements can be configured greater than ±6 dB(for example, ±10 dB or less).

By this means, the user terminal can be structured to performmeasurement operations for a TCC only when its quality is better than inan SCC and/or others, so that the user terminal's load can be reduced.Alternatively, since the level of reliability that is required to sendout reports can be achieved with a smaller number of samples, it ispossible to reduce the delays of reports even when, as mentionedearlier, the cycle of measurements is made longer. Note that the userterminal may be configured to measure TCCs by applying the sameconditions as those for SCCs, and report the measurement results of onlythose TCCs that fulfill limited conditions (for example, only those TCCswhere the lower-limit SINR value is greater than −6 dB (for example, +3dB) are subject to reporting).

As mentioned earlier, a case may occur where an unlicensed band isconfigured as a TCC. Consequently, assuming that measurement signals(discovery signals and/or others) may not be transmitted periodicallydepending on the result of DL LBT on the radio base station end, a userterminal may be structured to perform measurement operations based ondifferent predetermined conditions from those of PCCs and/or SCCs.

For example, a user terminal can be structured to make measurements in aTCC at predetermined timings based on commands from a licensed carrier(licensed CC). In this case, the radio base station can transmitdownlink control information (DCI) to the user terminal by using thelicensed band (which is, for example, the PCC or an SCC), and report themeasurement timings for the TCC. By this means, it is possible to reduceunnecessary measurement operations (or reporting operation) in the userterminal with respect to the TCC, and, furthermore, know the timings ofTCC measurements by the user terminal on the radio base station end.

Alternatively, a user terminal may perform measurement operations (blinddetection) by predicting the results of LBT in a TCC. For example, auser terminal may be structured to make measurements/send reports withrespect to a TCC when a measurement signal is detected from the TCC withpower (for example, received power) that is equal to or greater than apredetermined value. By this means, the user terminal is spared frommaking unnecessary measurement operations (or reporting operation) withrespect to the TCC.

Also, it is possible to structure a transmission point (radio basestation) that employs LBT to transmit a reference signal beforetransmitting a DL signal when the result of LBT shows that the channelis in the idle state (LBT_idle) and transmission is judged to bepossible. In this case, the user terminal can decide to transmit the DLsignal in a licensed band based on the reference signal (for example,the beacon reference signal (BRS)). Consequently, the user terminal maycontrol the measurement operations in a TCC based on beacon referencesignals that are received (for example, perform measurement operationsbased on BRSs that are received, etc.).

Alternatively, a user terminal may be structured to perform measurementoperations only with respect to a predetermined TCC (a predetermined TCCcell). Information about the predetermined TCC may be reported inadvance from the radio base station to the user terminal, or the userterminal may make decisions autonomously.

For example, a user terminal may be structured to perform measurementoperations only for TCCs (TCells) that are controlled under theconnecting radio base station, and not measure TCCs under other radiobase station (that is, limit the TCCs to make the target formeasurements). Alternatively, a structure may be employed here in whichthe radio base station reports information about TCCs to be subject tomeasurements in the user terminal via the PCC and/or an SCC in advance,and the user terminal performs measurement and/or reporting operationsonly with respect to the reported TCCs.

In this way, by allowing a user terminal to limit the TCCs to makemeasurements for, it is possible to reduce the increase of load in theuser terminal.

<Activated State>

When a TCC that is configured is in the activated state, a user terminalcan apply different receiving operations and/or measurement operationsfrom those for PCCs and/or SCCs, to the TCC (activated TCC).

In an existing system, a user terminal performs measurement operations(RRM measurements, CSI measurements, etc.) using downlink referencesignals such as cell-specific reference signals (CRSs), channel statemeasurement reference signal (CSI-RSs: Channel StateInformation-Reference Signals) and so on, with respect to SCCs in theactivated state. Also, the user terminal receives downlink controlinformation (DCI) from the SCCs in the activated state via downlinkcontrol channels.

Although, according to the present embodiment, a user terminal performsDL signal receiving operations and measurement operations with respectto TCCs in the activated state as well, it is possible to applyreceiving operations and/or measurement operations from those for SCCs.

For example, a user terminal can operate without the assumption that, inTCC, reference signals such as CRSs and others are transmitted in allsubframes. In this case, the user terminal can apply receivingoperations and/or measurement operations assuming that reference signalssuch as CRSs and others are transmitted at predetermined timings.

To be more specific, a user terminal can be structured to performreceiving operations for DL signals in a TCC (for example, the CRS, theCSI-RS, downlink control information, etc.) in predetermined timingsbased on commands from a licensed carrier (licensed CC). The radio basestation can transmit downlink control information (DCI) to the userterminal by using the licensed band (for example, the PCC or an SCC),and report the timings to receive DL signals in the TCC. By this means,it is possible to reduce unnecessary receiving operations for the TCC inthe user terminal, and, furthermore, know the receiving timings of theuser terminal in the TCC on the radio base station end.

Alternatively, a user terminal may perform measurement operations (blinddetection) by predicting the results of LBT in a TCC and so on. Forexample, a user terminal may be structured to perform receiving,measurement and/or reporting operations with respect to a TCC when areference signal such as the CRS or a downlink control signal (PDCCH) isreceived from the TCC with power (for example, received power) that isequal to or greater than a predetermined value. By this means, it ispossible to reduce unnecessary receiving operations and measurementoperations (or reporting operations) in the user terminal with respectto the TCC.

Also, a transmission point (radio base station) to employ LBT may bestructured to transmit a reference signal (BRS) before transmitting a DLsignal when the result of LBT shows that the channel is in the idlestate (LBT_idle) and transmission is judged to be possible. In thiscase, the user terminal can control the receiving operations and/ormeasurement operations in a TCC based on beacon reference signals thatare received.

Also, the present embodiment can use a different method to control theactivated state/deactivated state of a TCC to configure in a userterminal, from that used in existing SCCs.

In existing SCCs, a radio base station controls an SCC's configurationstate (activated state/deactivated state) based on the measurementresults of the SCC, reported from user terminals. By contrast, thepresent embodiment can control a TCC's configuration state based on apredetermined SCC. For example, when TCCs are configured in a userterminal, it is possible to configure the TCCs in association withpredetermined SCCs, and control each TCC's configuration state based onthe state of the corresponding SCC (activated state/deactivated state).

In this case, when configuring a TCC in the user terminal, the radiobase station can report information about the SCC that corresponds tothat TCC, to the user terminal. The user terminal can operate, assumingthat the SCC's reported configuration state and the corresponding TCC'sconfiguration state are the same. For example, when a predetermined SCCassumes the deactivated state (deactivated), the user terminal can judgethat the TCC to correspond to this SCC is also in the deactivated state.

In this way, by controlling the configuration state of a TCC based onanother cell (SCC), it is no longer necessary to report the TCCs'activated state/deactivated state to a user terminal separately. Also,the user terminal does not need to judge the configuration state of theTCC by using reports from the radio base station.

<Non-Configuration of Activated State/Deactivated State>

The present embodiment may be structured not to configure the activatedstate/deactivated state for a TCC. For example, a user terminal, inwhich a TCC is configured, can employ the measurement operations forTCCs, and, furthermore, perform receiving operations for DL data that istransmitted in the PDSCH based on commands from other CCs (the PCCand/or SCCs) and/or measurement operations that use CSI-RSs (see FIG.7A).

As for the measurement operations for TCCs, the same RRM measurements asin the PCC and/or SCCs, or simpler RRM measurements can be used (see,for example, FIG. 6). For the commands from the PCC and/or SCCs,cross-carrier scheduling to use downlink control information(PDCCH/EPDCCH) can be used.

With cross-carrier scheduling, when CA is used, allocation of a downlinkshared channel (PDSCH) and/or an uplink shared channel (PUSCH) of agiven CC (for example, a TCC) is commanded by using a downlink controlchannel (PDCCH and/or EPDCCH) of another CC (for example, the PCC and/oran SCC) (see FIG. 7B).

In FIG. 7B, downlink control information (DCI #2) to command allocationof the PDSCH and/or PUSCH transmitted in CC #2 (for example, a TCC) ismultiplexed over the PDCCH of another CC #1 (for example, the PCC or anSCC) and transmitted. In this case, to identify to which CC (CC #1 or CC#2) the PDSCH and/or the PUSCH commanded to be allocated by the downlinkcontrol information (DCI #2) that is multiplexed over the PDCCH of CC #1belongs to, a DCI configuration, in which a carrier indicator field(CIF) is provided, can be used.

For TCC DCI for user terminals, for example, DL assignments to commandreceipt of the PDSCH and UL grants to command transmission of the PUSCHand/or reporting of CSI can be used.

By this means, in a TCC, a user terminal does not have to receivedownlink control information (PDCCH) regularly, and therefore monitoringof DCI becomes can be made unnecessary. Also, by configuring a userterminal to perform channel state measurements (CSI measurements) basedon commands from the PCC and/or SCCs (for example, UL grants), it ispossible to make the regular CSI measurement operations in the userterminal unnecessary. As a result of this, even when a plurality of TCCsare configured in a user terminal, it is possible to reduce the increaseof the user terminal's load.

Second Example

With a second example, user terminal capability information (UEcapability), which is reported from a user terminal to a radio basestation when a TCC is configured apart from the PCC and SCCs will bedescribed.

As mentioned earlier, when a TCC, to which a user terminal appliesdifferent operations from those of the PCC and SCCs, is introduced, theuser terminal may execute CA using the PCC and the TCC (withoutconfiguring SCCs) (see FIG. 8). In this case, by making the measurementoperations and/or receiving operations for the TCC simpler than forSCCs, it is possible to allow even a user terminal that does not supportconventional CA to use a PCC and SCCs, to employ CA with a PCC and aTCC.

Consequently, to provide support for CA that uses TCCs, it is preferableto set forth new capability information (capability) for TCC CA. In thiscase, a user terminal can report the fact that the user terminal cansupport CA to use TCCs, and/or information about the TCCs that areavailable for use, to the radio base station.

To be more specific, the user terminal can report information about CCsthat can be configured (or activated) as TCCs at the same time, to theradio base station. For example, the user terminal can reportinformation to indicate the band that can be used in CA (carrierAggregation bandwidth class), as when SCCs are used, and, in addition,report to the radio base station which CCs can be configured (oractivated) as TCCs at the same time.

The TCC band is likely to be wide, and therefore it may be desirable toavoid configuring (or activating) all the TCCs at the same time.Consequently, in addition to reporting information (X_bandclass) thatindicates bands that can used as TCCs, it is preferable to report to theradio base station which CCs can be configured (or activated) as TCCs.For example, the user terminal reports information about CCs that can beconfigured (or activated) at the same time, to the radio base station,by using bitmap. Alternatively, the user terminal may report informationabout the number of CCs that can be configured (or activated) at thesame time, to the radio base station.

For example, the user terminal can report information about thecombination of TCCs that can used for a given bandwidth (band) and thenumber of CCs that can be configured (the maximum number of CCs), to theradio base station. Also, in addition to information about TCCs that canbe used, the user terminal can also report information about the duplexmode (FDD or TDD) that can be applied to each TCC to the radio basestation as capability information. In particular, if duplex modes arenot applied to TCCs on a fixed basis, it is effective if a user terminalreports which duplex modes can be applied to each TCC, to the radio basestation, in advance.

Also, when unlicensed bands are introduced, cases might occur whereevery country's laws and regulations require different functions to useunlicensed bands. Consequently, a user terminal may report to the radiobase station whether or not each country's laws and regulations providesupport for unlicensed bands (TCCs). In this case, it is preferable ifthe user terminal reports information about its capability (capability)to comply with the laws and regulations governing each country, inaddition information about TCCs that may be available for use. By thismeans, the radio base station can configure adequate TCCs in the userterminal.

(Structure of Radio Communication System)

Now, the structure of the radio communication system according to anembodiment of the present invention will be described below. In thisradio communication system, the radio communication methods according tothe embodiments of the present invention are employed. Note that theradio communication methods of the above-described embodiments may beapplied individually or may be applied in combination.

FIG. 9 is a diagram to show an example of a schematic structure of aradio communication system according to an embodiment of the presentinvention. Note that the radio communication system shown in FIG. 9 is asystem to incorporate, for example, an LTE system, super 3G, an LTE-Asystem and so on. In this radio communication system, carrieraggregation (CA) and/or dual connectivity (DC) to bundle a plurality ofcomponent carriers (PCC, SCC, TCC, etc.) into one can be used. Note thatthis radio communication system may be referred to as “IMT-Advanced,” ormay be referred to as “4G,” “5G,” “FRA” (Future Radio Access) and so on.

The radio communication system 1 shown in FIG. 9 includes a radio basestation 11 that forms a macro cell C1, and radio base stations 12 a to12 c that form small cells C2, which are placed within the macro cell C1and which are narrower than the macro cell C1. Also, user terminals 20are placed in the macro cell C1 and in each small cell C2.

The user terminals 20 can connect with both the radio base station 11and the radio base stations 12. The user terminals 20 may use the macrocell C1 and the small cells C2, which use different frequencies, at thesame time, by means of CA or DC. Also, the user terminals 20 can executeCA or DC by using at least six or more CCs (cells). For example, it ispossible to configure, in the user terminals, the macro cell C1 as thePCell (PCC) and the small cells C2 as SCells (SCCs) and/or TCells(TCCs). Also, for TCCs, licensed bands and/or unlicensed bands can beconfigured.

Between the user terminals 20 and the radio base station 11,communication can be carried out using a carrier of a relatively lowfrequency band (for example, 2 GHz) and a narrow bandwidth (referred toas, for example, an “existing carrier,” a “legacy carrier” and so on).Meanwhile, between the user terminals 20 and the radio base stations 12,a carrier of a relatively high frequency band (for example, 3.5 GHz, 5GHz and so on) and a wide bandwidth may be used, or the same carrier asthat used in the radio base station 11 may be used. Between the radiobase station 11 and the radio base stations 12 (or between two radiobase stations 12), wire connection (optical fiber, the X2 interface,etc.) or wireless connection may be established.

The radio base station 11 and the radio base stations 12 are eachconnected with a higher station apparatus 30, and are connected with acore network 40 via the higher station apparatus 30. Note that thehigher station apparatus 30 may be, for example, an access gatewayapparatus, a radio network controller (RNC), a mobility managemententity (MME) and so on, but is by no means limited to these. Also, eachradio base station 12 may be connected with higher station apparatus 30via the radio base station 11.

Note that the radio base station 11 is a radio base station having arelatively wide coverage, and may be referred to as a “macro basestation,” a “central node,” an “eNB” (eNodeB), a “transmitting/receivingpoint” and so on. Also, the radio base stations 12 are radio basestations having local coverages, and may be referred to as “small basestations,” “micro base stations,” “pico base stations,” “femto basestations,” “HeNBs” (Home eNodeBs), “RRHs” (Remote Radio Heads),“transmitting/receiving points” and so on. Hereinafter the radio basestations 11 and 12 will be collectively referred to as a “radio basestation 10,” unless specified otherwise. The user terminals 20 areterminals to support various communication schemes such as LTE, LTE-Aand so on, and may be either mobile communication terminals orstationary communication terminals.

In the radio communication system, as radio access schemes, OFDMA(Orthogonal Frequency Division Multiple Access) is applied to thedownlink, and SC-FDMA (Single-Carrier Frequency Division MultipleAccess) is applied to the uplink. OFDMA is a multi-carrier communicationscheme to perform communication by dividing a frequency band into aplurality of narrow frequency bands (subcarriers) and mapping data toeach subcarrier. SC-FDMA is a single-carrier communication scheme tomitigate interference between terminals by dividing the system band intobands formed with one or continuous resource blocks per terminal, andallowing a plurality of terminals to use mutually different bands. Notethat the uplink and downlink radio access schemes are by no meanslimited to the combination of these.

In the radio communication system 1, a downlink shared channel (PDSCH:Physical Downlink Shared CHannel), which is used by each user terminal20 on a shared basis, a broadcast channel (PBCH: Physical BroadcastCHannel), downlink L1/L2 control channels and so on are used as downlinkchannels. User data, higher layer control information and predeterminedSIBs (System Information Blocks) are communicated in the PDSCH. Also,MIBs (Master Information Blocks) and so on are communicated by the PBCH.

The downlink L1/L2 control channels include a PDCCH (Physical DownlinkControl CHannel), an EPDCCH (Enhanced Physical Downlink ControlCHannel), a PCFICH (Physical Control Format Indicator CHannel), a PHICH(Physical Hybrid-ARQ Indicator CHannel) and so on. Downlink controlinformation (DCI) including PDSCH and PUSCH scheduling information iscommunicated by the PDCCH. The number of OFDM symbols to use for thePDCCH is communicated by the PCFICH. HARQ delivery acknowledgementsignals (ACKs/NACKs) in response to the PUSCH are communicated by thePHICH. The EPDCCH may be frequency-division-multiplexed with the PDSCH(downlink shared data channel) and used to communicate DCI and so on,like the PDCCH.

Also, as downlink reference signals, cell-specific reference signals(CRSs), channel state measurement reference signals (CSI-RSs: ChannelState Information-Reference Signals), user-specific reference signals(DM-RSs: Demodulation Reference Signals) for use for demodulation andothers are included.

In the radio communication system 1, an uplink shared channel (PUSCH:Physical Uplink Shared CHannel), which is used by each user terminal 20on a shared basis, an uplink control channel (PUCCH: Physical UplinkControl CHannel), a random access channel (PRACH: Physical Random AccessCHannel) and so on are used as uplink channels. User data and higherlayer control information are communicated by the PUSCH. Also, downlinkradio quality information (CQI: Channel Quality Indicator), deliveryacknowledgment signals (HARQ-ACKs) and so on are communicated by thePUCCH. By means of the PRACH, random access preambles (RA preambles) forestablishing connections with cells are communicated.

<Radio Base Station>

FIG. 10 is a diagram to show an example of an overall structure of aradio base station according to one embodiment of the present invention.A radio base station 10 has a plurality of transmitting/receivingantennas 10, amplifying sections 102, transmitting/receiving sections103, a baseband signal processing section 104, a call processing section105 and a communication path interface 106. Note that thetransmitting/receiving sections 103 are comprised of transmissionsections and receiving sections.

User data to be transmitted from the radio base station 10 to a userterminal 20 on the downlink is input from the higher station apparatus30 to the baseband signal processing section 104, via the communicationpath interface 106.

In the baseband signal processing section 104, the user data issubjected to a PDCP (Packet Data Convergence Protocol) layer process,user data division and coupling, RLC (Radio Link Control) layertransmission processes such as RLC retransmission control, MAC (MediumAccess Control) retransmission control (for example, an HARQ (HybridAutomatic Repeat reQuest) transmission process), scheduling, transportformat selection, channel coding, an inverse fast Fourier transform(IFFT) process and a precoding process, and the result is forwarded toeach transmitting/receiving section 103. Furthermore, downlink controlsignals are also subjected to transmission processes such as channelcoding and an inverse fast Fourier transform, and forwarded to eachtransmitting/receiving section 103.

Each transmitting/receiving section 103 converts baseband signals thatare pre-coded and output from the baseband signal processing section 104on a per antenna basis, into a radio frequency band. The radio frequencysignals having been subjected to frequency conversion in thetransmitting/receiving sections 103 are amplified in the amplifyingsections 102, and transmitted from the transmitting/receiving antennas101.

For example, the transmitting/receiving sections 103 can transmitinformation about CCs that execute CA (for example, information about aCC to serve as a TCC, and so on). Also, the transmitting/receivingsections 103 can report receiving operation and/or measurement operationcommands in TCCs via downlink control information (PDCCH) of the PCCand/or SCCs, to the user terminals. For the transmitting/receivingsections 103, transmitters/receivers, transmitting/receiving circuits ortransmitting/receiving devices that can be described based on commonunderstanding of the technical field to which the present inventionpertains can be used.

Meanwhile, as for uplink signals, radio frequency signals that arereceived in the transmitting/receiving antennas 101 are each amplifiedin the amplifying sections 102. Each transmitting/receiving section 103receives uplink signals amplified in the amplifying sections 102. Thereceived signals are converted into the baseband signal throughfrequency conversion in the transmitting/receiving sections 103 andoutput to the baseband signal processing section 104.

In the baseband signal processing section 104, user data that isincluded in the uplink signals that are input is subjected to a fastFourier transform (FFT) process, an inverse discrete Fourier transform(IDFT) process, error correction decoding, a MAC retransmission controlreceiving process, and RLC layer and PDCP layer receiving processes, andforwarded to the higher station apparatus 30 via the communication pathinterface 106. The call processing section 105 performs call processingsuch as setting up and releasing communication channels, manages thestate of the radio base stations 10 and manages the radio resources.

The communication path interface section 106 transmits and receivessignals to and from the higher station apparatus 30 via a predeterminedinterface. Also, the communication path interface 106 transmits andreceives signals to and from neighboring radio base stations 10(backhaul signaling) via an inter-base station interface (for example,optical fiber, the X2 interface, etc.).

FIG. 11 is a diagram to show an example of a functional structure of aradio base station according to the present embodiment. Note that,although FIG. 11 primarily shows functional blocks that pertain tocharacteristic parts of the present embodiment, the radio base station10 has other functional blocks that are necessary for radiocommunication as well. As shown in FIG. 11, the baseband signalprocessing section 104 has a control section (scheduler) 301, atransmission signal generating section (generating section) 302, amapping section 303 and a received signal processing section 304.

The control section (scheduler) 301 controls the scheduling of (forexample, allocates resources to) downlink data signals that aretransmitted in the PDSCH and downlink control signals that arecommunicated in the PDCCH and/or the EPDCCH. Furthermore, the controlsection (scheduler) 301 also controls the scheduling of systeminformation, synchronization signals, paging information, CRSs, CSI-RSsand so on.

For an unlicensed CC (for example, a TCC), the control section 301controls the transmission of DL signals based on the result of DL LBT.When LBT is executed in the unlicensed band (TCC), the control section301 may control the result of this LBT to be reported to the userterminal in a licensed band (the PCC and/or an SCC). Also, in the TCC,the control section 301 can configure the transmission cycle of downlinkreference signals (for example, the CRS, the CSI-RS, etc.) longer thanin SCCs, or configure the transmission cycle shorter than in SCCs.

Also, the control section 301 controls the scheduling of uplinkreference signals, uplink data signals that are transmitted in thePUSCH, uplink control signals that are transmitted in the PUCCH and/orthe PUSCH, random access preambles that are transmitted in the PRACH,and so on. Note that, for the control section 301, a controller, acontrol circuit or a control device that can be described based oncommon understanding of the technical field to which the presentinvention pertains can be used.

The transmission signal generating section 302 generates DL signalsbased on commands from the control section 301 and outputs these signalsto the mapping section 303. For example, the transmission signalgenerating section 302 generates DL assignments, which report downlinksignal allocation information, and UL grants, which report uplink signalallocation information, based on commands from the control section 301.Also, the downlink data signals are subjected to a coding process and amodulation process, based on coding rates and modulation schemes thatare determined based on channel state information (CSI) from each userterminal 20 and so on. Note that, for the transmission signal generatingsection 302, a signal generator, a signal generating circuit or a signalgenerating device that can be described based on common understanding ofthe technical field to which the present invention pertains can be used.

The mapping section 303 maps the downlink signals generated in thetransmission signal generating section 302 to predetermined radioresources based on commands from the control section 301, and outputsthese to the transmitting/receiving sections 103. Note that, for themapping section 303, mapper, a mapping circuit or a mapping device thatcan be described based on common understanding of the technical field towhich the present invention pertains can be used.

The received signal processing section 304 performs the receivingprocesses (for example, demapping, demodulation, decoding and so on) ofthe UL signals that are transmitted from the user terminal (for example,delivery acknowledgement signals (HARQ-ACKs), data signals that aretransmitted in the PUSCH, random access preambles that are transmittedin the PRACH, and so on). The processing results are output to thecontrol section 301.

Also, by using the received signals, the received signal processingsection 304 may measure the received power (for example, the RSRP(Reference Signal Received Power)), the received quality (for example,the RSRQ (Reference Signal Received Quality)), channel states and so on.Alternatively, the received signal processing section 304 may execute DLLBT before DL signals are transmitted. Note that the measurement resultsin the received signal processing section 304 may be output to thecontrol section 301. Note that a measurement section to perform themeasurement operations may be provided apart from the received signalprocessing section 304.

The receiving process section 304 can be constituted by a signalprocessor, a signal processing circuit or a signal processing device,and a measurer, a measurement circuit or a measurement device that canbe described based on common understanding of the technical field towhich the present invention pertains.

<User Terminal>

FIG. 12 is a diagram to show an example of an overall structure of auser terminal according to the present embodiment. A user terminal 20has a plurality of transmitting/receiving antennas 201 for MIMOcommunication, amplifying sections 202, transmitting/receiving sections203, a baseband signal processing section 204 and an application section205. Note that the transmitting/receiving sections 203 may be comprisedof transmission sections and receiving sections.

Radio frequency signals that are received in a plurality oftransmitting/receiving antennas 201 are each amplified in the amplifyingsections 202. Each transmitting/receiving section 203 receives thedownlink signals amplified in the amplifying sections 202. The receivedsignals are subjected to frequency conversion and converted into thebaseband signal in the transmitting/receiving sections 203, and outputto the baseband signal processing section 204.

The transmitting/receiving sections 203 can report the user terminal'scapability information (capability) to the radio base station. Forexample, the transmitting/receiving sections 203 transmits informationabout TCCs that can be used at the same time (for example, informationabout the combination of TCCs), in addition to information about thefrequencies in which TCCs can be used, to the radio base station. Also,the transmitting/receiving sections 203 may transmit information aboutthe duplex mode (FDD or TDD) that is applicable to each third CC thatcan be configured. Note that, for the transmitting/receiving sections203, transmitters/receivers, transmitting/receiving circuits ortransmitting/receiving devices that can be described based on commonunderstanding of the technical field to which the present inventionpertains can be used.

In the baseband signal processing section 204, the baseband signal thatis input is subjected to an FFT process, error correction decoding, aretransmission control receiving process, and so on. Downlink user datais forwarded to the application section 205. The application section 205performs processes related to higher layers above the physical layer andthe MAC layer, and so on. Furthermore, in the downlink data, broadcastinformation is also forwarded to the application section 205.

Meanwhile, uplink user data is input from the application section 205 tothe baseband signal processing section 204. The baseband signalprocessing section 204 performs a retransmission control transmissionprocess (for example, an HARQ transmission process), channel coding,pre-coding, a discrete Fourier transform (DFT) process, an IFFT processand so on, and the result is forwarded to each transmitting/receivingsection 203. The baseband signal that is output from the baseband signalprocessing section 204 is converted into a radio frequency band in thetransmitting/receiving sections 203. The radio frequency signals thatare subjected to frequency conversion in the transmitting/receivingsections 203 are amplified in the amplifying sections 202, andtransmitted from the transmitting/receiving antennas 201.

FIG. 13 is a diagram to show an example of a functional structure of auser terminal according to the present embodiment. Note that, althoughFIG. 13 primarily shows functional blocks that pertain to characteristicparts of the present embodiment, the user terminal 20 has otherfunctional blocks that are necessary for radio communication as well. Asshown in FIG. 13, the baseband signal processing section 204 provided inthe user terminal 20 has a control section 401, a transmission signalgenerating section 402, a mapping section 403, a received signalprocessing section 404 and a measurement section 405.

The control section 401 acquires the downlink control signals (signalstransmitted in the PDCCH/EPDCCH) and downlink data signals (signalstransmitted in the PDSCH) transmitted from the radio base station 10,from the received signal processing section 404. The control section 401controls the generation of uplink control signals (for example, deliveryacknowledgement signals) and uplink data signals based on the downlinkcontrol signals, the results of deciding whether or not retransmissioncontrol is necessary for the downlink data signals, and so on.

The control section 401 can control the transmission signal generatingsection 402, the mapping section 403, the received signal processingsection 404 and the measurement section 405. For example, when the userterminal employs CA that uses TCCs (see FIG. 5 and FIG. 8), the controlsection 401 applies control so that receiving operations and/ormeasurement operations that are different from those of the PCC and/orSCCs are applied to the TCCs.

For example, the control section 401 can configure the measurementperiod in the TCCs shorter than the measurement cycle in SCCs (see FIG.6A), and/or configure the measurement cycle in the TCCs longer than themeasurement cycle in SCCs. Alternatively, the control section 401 canconfigure the lower limit value of the SINR (Signal to Interference plusNoise power Ratio) of DL signals that is to be detected uponmeasurements for the TCCs higher than the lower-limit SINR value of DLsignals to be detected in measurements for SCCs (see FIG. 6B).

The control section 401 can control the measurement section 405 to makemeasurements for a TCC when a command is received from the PCC and/orSCCs or when received power that is equal to or greater than apredetermined value is detected from the TCC. Alternatively, the controlsection 401 may control the measurement section 405 to limit the TCCs tosubject to measurements to the TCCs under the radio base station towhich the user terminal is connected.

The control section 401 may decide the state of a TCC that is configured(the activated state or the deactivated state) based on the state of thePCC or an SCC that is associated in advance with this TCC, and controlthe receiving operations and/or measurement operations accordingly.

Also, the control section 401 can control the data signal receivingoperations and/or measurement operations that use channel statemeasurement reference signals for TCCs based on cross-carrier schedulingfrom the PCC and/or SCCs (see FIG. 7).

For the control section 401, a controller, a control circuit or acontrol device that can be described based on common understanding ofthe technical field to which the present invention pertains can be used.

The transmission signal generating section 402 generates UL signalsbased on commands from the control section 401 and outputs these signalsto the mapping section 403. For example, the transmission signalgenerating section 402 generates uplink control signals such as deliveryacknowledgement signals (HARQ-ACKs), channel state information (CSI) andso on, based on commands from the control section 401.

Also, the transmission signal generating section 402 generates uplinkdata signals based on commands from the control section 401. Forexample, when a UL grant is included in a downlink control signal thatis reported from the radio base station 10, the control section 401commands the transmission signal generating section 402 to generate anuplink data signal. Also, the transmission signal generating section 402generates UL signals from the results of measurements in the measurementsection 405, based on commands from the control section 401. For thetransmission signal generating section 402, a signal generator, a signalgenerating circuit or a signal generating device that can be describedbased on common understanding of the technical field to which thepresent invention pertains can be used.

The mapping section 403 maps the uplink signals (uplink control signalsand/or uplink data) generated in the transmission signal generatingsection 402 to radio resources based on commands from the controlsection 401, and output the result to the transmitting/receivingsections 203. For the mapping section 403, mapper, a mapping circuit ora mapping device that can be described based on common understanding ofthe technical field to which the present invention pertains can be used.

The received signal processing section 404 performs the receivingprocesses (for example, demapping, demodulation, decoding and so on) ofthe DL signals (for example, downlink control signals that aretransmitted from the radio base station in the PDCCH/EPDCCH, downlinkdata signals transmitted in the PDSCH, and so on). The received signalprocessing section 404 outputs the information received from the radiobase station 10, to the control section 401. The received signalprocessing section 404 outputs, for example, broadcast information,system information, RRC signaling, DCI and so on, to the control section401.

The received signal processing section 404 can control the DL signalreceiving operations based on commands from the control section 401. Forexample, when a TCC is configured in the user terminal, the receivedsignal processing section 404 can perform receiving operations that aredifferent from those of the PCC and/or SCCs, based on commands from thecontrol section 401 (see FIG. 7). Note that, for the received signalprocessing section 404, a signal processor/measurer, a signalprocessing/measurement circuit or a signal processing/measurement devicethat can be described based on common understanding of the technicalfield to which the present invention pertains can be used. Also, thereceived signal processing section 404 can constitute the receivingsection according to the present invention.

The measurement section 405 makes measurements (for example, RRMmeasurements, CSI measurements, etc.) by using the DL signals that arereceived (for example, the CRS, the CSI-RS, etc.). To be more specific,the measurement section 405 can measure the received power (for example,the RSRP (Reference Signal Received Power)), the received quality (RSRQ(Reference Signal Received Quality)), channel states and so on by usingthe DL reference signals that are received (for example, the CRS, theCSI-RS, etc.). The processing results are output to the control section401.

The measurement section 405 can control the DL signal measurementoperations based on commands from the control section 401. For example,when a TCC is configured in the user terminal, the measurement section405 can perform different measurement operations from those for the PCCand/or SCCs, based on commands from the control section 401 (see FIG. 6and FIG. 7). For the received signal processing section 404, a signalprocessor/measurer, a signal processing/measurement circuit or a signalprocessing/measurement device that can be described based on commonunderstanding of the technical field to which the present inventionpertains can be used.

Note that the block diagrams that have been used to describe the aboveembodiments show blocks in functional units. These functional blocks(components) may be implemented in arbitrary combinations of hardwareand software. Also, the means for implementing each functional block isnot particularly limited. That is, each functional block may beimplemented with one physically-integrated device, or may be implementedby connecting two physically-separate devices via radio or wire andusing these multiple devices.

For example, part or all of the functions of radio base stations 10 anduser terminals 20 may be implemented using hardware such as ASICs(Application-Specific Integrated Circuits), PLDs (Programmable LogicDevices), FPGAs (Field Programmable Gate Arrays), and so on. Also, theradio base stations 10 and user terminals 20 may be implemented with acomputer device that includes a processor (CPU), a communicationinterface for connecting with networks, a memory and a computer-readablestorage medium that holds programs.

Here, the processor and the memory are connected with a bus forcommunicating information. Also, the computer-readable recording mediumis a storage medium such as, for example, a flexible disk, anopto-magnetic disk, a ROM, an EPROM, a CD-ROM, a RAM, a hard disk and soon. Also, the programs may be transmitted from the network through, forexample, electric communication channels. Also, the radio base stations10 and user terminals 20 may include input devices such as input keysand output devices such as displays.

The functional structures of the radio base stations 10 and userterminals 20 may be implemented with the above-described hardware, maybe implemented with software modules that are executed on the processor,or may be implemented with combinations of both. The processor controlsthe whole of the user terminals by running an operating system. Also,the processor reads programs, software modules and data from the storagemedium into the memory, and executes various types of processes. Here,these programs have only to be programs that make a computer executeeach operation that has been described with the above embodiments. Forexample, the control section 401 of the user terminals 20 may be storedin the memory and implemented by a control program that operates on theprocessor, and other functional blocks may be implemented likewise.

Now, although the present invention has been described in detail above,it should be obvious to a person skilled in the art that the presentinvention is by no means limited to the embodiments described herein.For example, the above-described embodiments may be used individually orin combinations. The present invention can be implemented with variouscorrections and in various modifications, without departing from thespirit and scope of the present invention defined by the recitations ofclaims. Consequently, the description herein is provided only for thepurpose of explaining examples, and should by no means be construed tolimit the present invention in any way.

The disclosure of Japanese Patent Application No. 2015-030784, filed onFeb. 19, 2015, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

1. A user terminal that communicates with a radio base station by means of carrier aggregation using a plurality of component carriers (CCs), the user terminal comprising: a receiving section that receives DL signals transmitted from each CC; a measurement section that makes measurements by using the DL signals; and a control section that controls receiving operations in the receiving section and measurement operations in the measurement section, wherein, when a plurality of CCs, including at least a first CC, which corresponds to a primary CC of an existing system, and a third CC, which is different from the first CC and a second CC that corresponds to a secondary CC of the existing system, are configured, the control section applies, to the third CC, receiving operations and/or measurement operations that are different from those of the second CC.
 2. The user terminal according to claim 1, wherein the control section configures a measurement period for the third CC shorter than a measurement period for the second CC configures a measurement cycle for the third CC longer than a measurement cycle for the second CC, and/or configures a lower limit value for an SINR (Signal to Interference plus Noise power Ratio) of DL signals to be detected in measurements for the third CC higher than a lower-limit SINR value of DL signals to be detected in measurements for the second CC.
 3. The user terminal according to claim 1, wherein the control section makes measurements for the third CC when a command from the first CC and/or the second CC is received, or when received power that is equal to or greater than a predetermined value is detected from the third CC.
 4. The user terminal according to claim 1, wherein the control section limits third CCs to make measurements for, to third CCs that are controlled under a radio base station to which the user terminal is connected.
 5. The user terminal according to claim 1, wherein the control section judges whether the third CC that is configured is in an activated state or a deactivated state based on a state of a second CC that is associated with the third CC, and controls the receiving operations and/or the measurement operations.
 6. The user terminal according to claim 1, wherein, based on cross-carrier scheduling from the first CC and/or the second CC, the control section controls DL data receiving operations and/or measurement operations that use channel state measurement reference signals, for the third CC.
 7. The user terminal according to claim 1, further comprising a transmission section that transmits information about third CCs that can be configured at the same time, to a radio base station.
 8. The user terminal according to claim 7, wherein the transmission section transmits information about duplex modes that are applicable to third CCs that can be configured.
 9. A radio base station that communicates with a user terminal that employs carrier aggregation using a plurality of component carriers (CCs), the radio base station comprising: a transmission section that transmits DL signals in each CC; and a control section that controls transmission of the DL signals, wherein, when a plurality of CCs, including at least a first CC, which corresponds to a primary CC of an existing system, and a third CC, which is different from the first CC and a second CC that corresponds to a secondary CC of the existing system, are configured, the control section controls receiving operations and/or measurement operations of the user terminal in the third CC, by using DL signals transmitted from the first CC and/or the second CC.
 10. A radio communication method in a user terminal that communicates with a radio base station by means of carrier aggregation using a plurality of component carriers (CCs), the radio communication method comprising the steps of: receiving DL signals transmitted from each CC; and making measurements by using the DL signals, wherein, when a plurality of CCs, including at least a first CC, which corresponds to a primary CC of an existing system, and a third CC, which is different from the first CC and a second CC that corresponds to a secondary CC of the existing system, are configured, receiving operations and/or measurement operations that are different from those of the second CC are applied to the third CC. 